My wife and I will be staying in Vernazza in September for four nights. We will hike the CT one day. In addition, I was thinking about taking a train tour of the Italian Riviera as day trips. Perhaps a trip to Genoa for the day. Another day to visit some of the smaller villages along the way. I have a few questions:
1. Is this practical?
2. Any hidden must see gems?
3. Any tips?

I took a short day trip from Levanto just beyond to Portofino and walked up to Costello Brown I believe it was called. It was a lovely afternoon and an easy trip from CT. The view from the top of Costello is breathtaking of the whole bay of Portofino below. Barb Cabot

If we have friends that are staying with us who have not been to the area before we usually take the train to Rapallo. After a stop here we the take the boat direct to Portofino where following sightseeing and windowshopping stop at La Gritta for drinks. From Portofino we get the 82 bus to SML and aperitivi in Master before getting the train back to La spezia

It is very practical and very doable, but keep in mind that you may not see as much of the beautiful coastal scenery as you think. There are many long tunnels along the coast. You might think you are on the subway for some of the trip. There are many great towns between the CT and Genova and don't forget Portovenere just south of Riomaggiore. Catch one of the tour boats from the CT to get there. I am not a fan of Portofino. Reminds me of a Hollywood version of an Italian coastal town. Sestri Levante, Rapallo, Santa Margherita, and Camogli are some of my favorites.

Portovenere should be at the top of your list (ok IMO)!

Also Camogli is very nice.

Genova is one of the most underrated cities in Italy: yes, a rough exterior but incredible on the inside (centro, port, Maddalena, Strada Nuova and oh the food!).

All easy day trips from the CT (although Portovenere would need to be visited by boat, which again IMO is the best way to do and see it all.